More About Prechamber Inserts

[ktzdsl]

Libbydiesel/all -

here's my data:
Casting #068 103 373E (original German head from 1983 Jetta 1.6TD)
Mechanical 12mm studs, TD 1.6 w/Garrett T3
Magnetic status unknown, but likely inconel
All cups cracked, most in two places
32mm diameter
No dimples.

The precups seemed tight in the head, but cracks in all four, 221,000 miles on the head, and my plan to run 15-18 peak psi boost,
led me to replace them with interference sized Eurocar Togliani cups (32.5mm).   I had the head bored with approx .002 interference fit,
heated the head to 350F, froze the precups, and then staked their perimeter in 5 or 6 places away from headgasket areas.  Engine
is still on the stand for install later this spring. 

How much did it cost to have the head bored for the oversized precups? Thanks.

[RabbitJockey]

here was the prechambers from my 1.6td its a true td solid lifter head and had no cracks between the valves, i still didn't install the head, are these safe???


number 1



number 2



number 3



and cylinder number 4

[libbydiesel]

There is NO WAY I'd run it like that.  The #2 cup looks especially bad.  In 1,000 miles the front part could fall into the cylinder. 

[745 turbogreasel]

I'm thinking the stickout is probably a bit shy too.

[RabbitJockey]

I'm thinking the stickout is probably a bit shy too.

they are flush, the machine shop milled the head for no reason, they made it sound like they do that on most heads they get in to make sure no one comes back.  its more of a pita problem for me tho and i know this head was flat and true.  but i griped about that on here before haha.

[TylerDurden]

Recently saw a comment on NOT staking/peening precups... no comment on why not. Any thoughts?


Also measured a Topline 1.6 mech head: 32mm precups. (No casting number AFAICT.)

[hillfolk'r]

My cyl head guy recommended doing it on the block/deck grinder vs the normal cutting machine. He said the chambers are hard to cut and the grinder does a nicer finish

[745 turbogreasel]

You can see in pics 1 and 3 where the machine skipped  off the precup.  looks like it maybe wipes them  to the left in the bore as it hangs momentarily on the hard leading edge too.

[92EcoDiesel Jetta]

To me, every pic shows grinding marks which shows the entire head was skimmed with the pre chambers installed.

I remember when I had my head from the 92 Eco pressure tested after blowing a head gasket, the shop wanted to skim the head flat with a sander for $60. I told them NO! NO!NO!, the head warpage is within spec, leave it the f**K alone.

here was the prechambers from my 1.6td its a true td solid lifter head and had no cracks between the valves, i still didn't install the head, are these safe???


number 1



number 2



number 3



and cylinder number 4

[Rock3tman]

ktzdsl - The charge for the prechamber machining was part of the entire head rebuild...I recall less than $100.00 for the custom sized
interference cutter and installation work.

RabbitJockey - I wouldn't run prechambers as cracked as those either in any sort of nice rig: my $.02 FWIW.

attached are photos of my 1.6TD prechambers from Eurocar Togliani showing how staking would flow a little material under the face of the
prechamber to add a little security to their installation.

[RabbitJockey]

Hmm maybe ill see if there's an actual diesel shop around here who could install those for me with proper protrusion

[CrazyAndy]

So that ball in the prechamber side would push some metal in the head around?  How exactly does that improve the security of the installation?

[Gizmoman]

So that ball in the prechamber side would push some metal in the head around?  How exactly does that improve the security of the installation?

I looked at my old head which I removed all four cups from. There is a groove machined in the cup bore that matches the nipple. It defiantly isn't gouged out as I had first thought as well. Apparently it's there to insure proper alignment.
In my opinion, it would take some serious staking to move the aluminum at that depth. If I were putting new "over-sized" cups in, I'd heat the head and freeze the cup which I think was mentioned in here somewhere already. I believe they mentioned an. 002" press fit but there must be a specification somewhere.